Seeing the Forest Through the Weed.

1st let me tip my hat to Colorado’s legislature in allowing marijuana / cannabis to be legally sold, as it should of been to anyone who wanted to learn first hand it is not dangerous as our trusting government wanted you to believe. Colorado has it’s right and I personally am impressed that finally a state stood up for it’s citizens rights to choose what they put into their bodies, be it for medicinal or recreational.

I also noticed from media coverage there was a short supply, although there was plenty of warning, the demand was more than anyone anticipated. That being said, it’s time t5o look at some of the impacts this will create.

One, supply is behind demand, this makes it easier to control prices and limits the amount available, as shown on Colorado’s opening day.

Two, the demand on electric from the use of 1000 watt H.P.S. or Medal Halogen lighting is nothing short of a demand on utilities, this demand will be passed on to the consumer as everything else is. Not to mention the electrical cost to vent and cool these rooms down, again an added cost to be passed on to the purchaser of their product.

As a small grower for personal medication I found using these type of lights did not allow me to feasibly grow, in fact I was just below what it cost from the shops. My electric bill usually ran around $350.00 per month. What I found that decreased my costs and still allowed me to get the full spectrum available were Inda-Gro’s induction lighting products. Using a P.A.R. 420 in fact cut my electric bill in half. For one. it uses less electric (420 watts) vs 1000. Ventilation costs removed due to low heat output from these induction bub’s, All that is needed is a oscillating fan for plant movement, not to mention the carbon footprints are reduced greatly, making Inda-Gro environmentally safe, personally my opinion the safest available.

Another major fact these bulbs last for 100.000 hrs without having to change bulbs, at $100.00 per bulb with changing every six months alone could purchase one of these Inda-Gro lights!


Measuring Plant Lighting


There are a number of ways to measure indoor plant lighting levels. As such there remains considerable debate as to which method
provides the gardener with the best information in determining if the light source is providing the ideal wavelengths and intensities to optimize plant response. While the debate swirls it ultimately will always come down to our plants response to those spectrums and intensities. We recognize that the complexities of understanding and choosing which technology, or lamp, is best suited for gardening with indoor artificial lighting can be confusing. We publish our lamps output data in a format that you may not be familiar with, but we believe it offers the gardener a better opportunity to determine how much energy a lamp emits between 400 - 700 nm relative to generally accepted photosynthetic absorption regions. As you can see by this Net Action Absorption Chart, what is believed to be the areas of greatest importance for a lamp’s energy to meet peak chlorophyll absorption points would be in the Vegetative Regions (Ultraviolet-Blue) and Flowering Regions (Red-Far Red). Less energy is required of the Carotenoid region (Green-Yellow) but as you can see there is still need for the lamp to emit within this region.

Beer’s Law

An essential piece of information about any molecular species is how much of it is present. Quantitative measures of concentration are one of the cornerstones of biological science. Of all the methods that have been devised for measuring concentration, by far the most widely applied is absorption spectrophotometry. In this technique, the amount of light that a sample absorbs at a particular wavelength is measured and used to determine the concentration of the sample by comparison with appropriate standards or reference data. The most useful measure of light absorption is the absorbance (A), also commonly called the optical density (OD) (Web Figure 7.1.A). The absorbance is defined asA = log I0 / I where I0 is the intensity of light that is incident on the sample and I is the intensity of light that is transmitted by the sample.

Web Figure 7.1.A   Definition of absorbance. A monochromatic incident light beam of intensity I0traverses a sample contained in a cuvette of length (l). Some of the light is absorbed by the chromophores in the sample, and the intensity of light that emerges is I.

The absorbance of a sample can be related to the concentration of the absorbing species through Beer’s law:


A = ε cl


where c is concentration, usually measured in moles per liter; l is the length of the light path, usually 1 cm; and ε is a proportionality constant known as the molar extinction coefficient, with the units of liters per mole per centimeter. The value of ε is a function of both the particular compound being measured and the wavelength. Chlorophylls typically have an ε value of about 100,000 L mol–1 cm–1. When more than one component of a complex mixture absorbs at a given wavelength, the absorbances due to the individual components are generally additive.

The Spectrophotometer

The absorbance is measured by an instrument called a spectrophotometer (Web Figure 7.1.B). The essential parts of a spectrophotometer include a light source, a wavelength selection device such as a monochromator or filter, a sample chamber, a light detector, and a readout device, usually also include a computer, which is used for storage and analysis of the spectra. The most useful machines scan the wavelength of the light that is incident on the sample and produce, as output, spectra of absorbance versus wavelength, such as those shown in textbook Figure 7.7.

Web Figure 7.1.B   Schematic diagram of a spectrophotometer. The instrument consists of a light source, a monochromator that contains a wavelength selection device such as a prism, a sample holder, a photodetector, and a recorder or computer. The output wavelength of the monochromator can be changed by rotation of the prism; the graph of absorbance versus wavelength is called a spectrum. (Click image to enlarge.)

Action Spectra

The use of action spectra has been central to the development of our current understanding of photosynthesis. An action spectrum is a graph of the magnitude of the biological effect observed as a function of wavelength. Examples of effects measured by action spectra are oxygen evolution (Web Figure 7.1.C) and hormonal growth responses due to the action of phytochrome (see Chapter 17 of the textbook). Often an action spectrum can identify the chromophore responsible for a particular light-induced phenomenon. Action spectra were instrumental in the discovery of the existence of the two photosystems in O2-evolving photosynthetic organisms.

Web Figure 7.1.C   An action spectrum compared to an absorption spectrum. The absorption spectrum is measured as shown in Web Figure 7.1.B. An action spectrum is measured by plotting a response to light such as oxygen evolution, as a function of wavelength. If the pigments used to obtain the absorption spectrum are the same as those that cause the response, the absorption and action spectra will match. In the example shown here, the action spectrum for oxygen evolution matches the absorption spectrum of intact chloroplasts quite well, indicating that light absorption by the chlorophylls mediates oxygen evolution. Discrepancies are found in the region of carotenoid absorption, from 450 to 550 nm, indicating that energy transfer from carotenoids to chlorophylls is not as effective as energy transfer between chlorophylls.

Some of the first action spectra were measured by T. W. Engelmann in the late 1800s (Web Figure 7.1.D). Engelmann used a prism to disperse sunlight into a rainbow that was allowed to fall on an aquatic algal filament. A population of O2-seeking bacteria was introduced into the system. The bacteria congregated in the regions of the filaments that evolved the most O2. These were the regions illuminated by blue light and red light, which are strongly absorbed by chlorophyll. Today, action spectra can be measured in room-sized spectrographs in which the scientist enters a huge monochromator and places samples for irradiation in a large area of the room bathed by monochromatic light. But the principle of the experiment is the same as that of Engelmann’s experiments.

Web Figure 7.1.D   Schematic diagram of the action spectrum measurements by T. W. Engelmann. Engelmann projected a spectrum of light onto the spiral chloroplast of the filamentous green algaSpirogyra and observed that oxygen-seeking bacteria introduced into the system collected in the region of the spectrum where chlorophyll pigments absorb. This action spectrum gave the first indication of the effectiveness of light absorbed by accessory pigments in driving photosynthesis.

Difference Spectra

An important technique in studies of photosynthesis is light-induced difference spectroscopy, which measures changes in absorbance (Web Figure 7.1.E). In this technique, bright light, often called actinic light, is used to illuminate a sample, while a dim beam of light is used to measure the absorbance of the sample at wavelengths other than that of the actinic beam. In this way a difference spectrum is obtained, which represents the changes in the absorption spectrum of the sample induced by illumination with the actinic light. Absorption bands that disappear upon illumination appear as negative peaks; new bands that appear upon illumination appear as positive peaks. Difference spectra give important clues to the identity of molecular species participating in the photoreactions of photosynthesis. The difference spectrum of the photooxidation of P700 (a chlorophyll that absorbs light of wavelength 700 nm

Grow lamp manufacturers produce Spectral Distribution Graphs for their lamps that graphically depict where the lamp will output wavelengths and in what intensities those wavelengths will emit. This works well in allowing the consumer to determine the lamps spectral output characteristics. The gardener can then decide if that particular lamp would work best for the type of plant being grown, specific growth cycles or if the spectrum is broad enough to take the plants from a vegetative thru a flowering state utilizing a single lamp. In determining the proper lamp to purchase, the gardener will sometimes mistakenly rely on numerically driven data such as a comparison of lumen output, lumen/watt, kelvin, lux, and μmole ratings to name a few.
For plant lighting comparisons, each of these values will at best give incomplete information and at its worse, will provide you with information that is mostly irrelevant to what your plants actually require from the lamp.
A more informed approach relies on a review of the manufacturer‟s spectral distribution graph. Once installed, the gardener will still want to measure light intensity to have complete lamp performance data. These types of field intensity measurements are usually
made with a modestly priced PAR meter which has been calibrated to the sun and not the artificial light source being measured.
Which leads us to, why we do not publish our lamp output data based on: Lumens, Lumens/Watt, Lux or Foot Candles-These
are all measurement terms that by definition use light meters which reference intensities adjusted to the human photopic luminosity function. They have little bearing on how a plant will respond to the intensities being emitted in visual regions.
Kelvin–This is another human visual standard that references how the light appears overall to the eye with 555 nm being peak visual sensitivity and 510/610nm being ½ peak visual sensitivity As higher Kelvin value imply, more blue to red ratio and lower Kelvin values would indicate a greater red to blue ratio . Basing your grow lamp decision based on how much visual red or blue a lamp emits is
not a good means of determining if that lamp is meeting the actual absorbance regions. μMole-This value is attained by using a PAR meter which is a better meter for reading plant intensity values in that it is not correcting for human photopic luminosity function, like a meter reading lumens, lux or footcandles will do, it still has some of its own issues.

Tuesday Night’s Free Meal

This Tuesday night, at 6pm as always Plymouth Congregational Church offer’s to it’s community monthly free feeding. As some of our readers know the last Tuesday of each month Plymouth Congregational Church opens it’s doors to the public and helps…